1. Field of the Invention
The present invention relates to a lens barrel having a linear guide mechanism for guiding a linear moving barrel to which a shutter unit is fixed, along an optical axis using a linear guiding member which allows the linear moving barrel to move along the optical axis while preventing the same from rotating about the optical axis.
2. Description of the Related Art
A conventional lens-shutter type of zoom camera having a linear guide mechanism is well known. In such a conventional camera, a zoom lens barrel of the camera is provided having a shutter unit therein, and a photographic lens element is supported on the shutter unit. When the zoom lens barrel is driven to advance from or retract into the camera body to effect zooming, the linear guide mechanism allows the shutter unit and the photographic lens element to move along an optical axis while preventing the shutter unit and the photographic lens element from rotating about the optical axis. A specific type of such a conventional linear guide mechanism having a linear moving barrel and a linear guide member is well-known. The linear moving barrel supports the shutter unit therein and is driven to move along the optical axis. The linear guide member allows the linear moving barrel to move along the optical axis while preventing the linear moving barrel from rotating about the optical axis. The linear guide member is provided with an annular base and a plurality of guide legs formed integral with the annular base. Each of the guide legs extends from the annular base in a direction of the optical axis. A plurality of linear guide slots are formed on a fixing member for fixing the shutter unit to the linear moving barrel. The aforementioned plurality of guide legs respectively and slidably engage with the plurality of linear guide slots, so that the shutter unit is guided linearly along the optical axis.
In such a conventional linear guide mechanism, it is necessary to provide such a fixing member, having the plurality of linear guide slots, separate from the shutter unit, thus increasing the number of components of the zoom lens barrel and making it difficult to realize a compact and lightweight zoom lens barrel.
Furthermore, since the aforementioned linear guide member, having the annular base and the plurality of guide legs, is usually made of a synthetic resin, one or more of the plurality of guide legs may be elastically bent inwardly (i.e., toward the optical axis) by a force applied to the leg or legs during the time the zoom lens barrel is driven to move to effect zooming. In the case that the leg or legs is bent by a large amount, the possibility exists that the leg or legs slips off the corresponding linear guide slot. In order to prevent the occurrence of such a problem, it is necessary to provide a device which restrains or prevents the leg or legs from being bent inwardly, so as to prevent the same from slipping off the linear guide slot. In a conventional linear guide mechanism, such a device is provided on a separate member from the shutter unit, thus increasing the number of components of the zoom lens barrel and making it difficult to realize a compact and lightweight zoom lens barrel.